双层膜法探究PEG膜厚对PLA球晶生长速率的影响

Effect of Thickness of Poly(ethyleneglycol)Film on Spherulitic Growth Rates for Polylactide by Layer-By-Layer Film Method

制备了一系列聚乙二醇膜厚不同的聚乙二醇(PEG)/聚乳酸(PLA)双层膜样品。利用偏光显微镜(POM)、差式扫描量热仪(DSC)研究了不同膜厚的PEG在不同结晶温度下,对下层聚乳酸球晶的晶体形貌、球晶生长速率及热力学性能的影响。研究表明,覆盖熔融的PEG后,PLA球晶的生长速率得到明显提高,并且,当PEG膜厚为2μm时,PLA球晶的生长速率达到最快,为23.0μm/min,比纯聚乳酸的最快球晶生长速率(0.5μm/min)高出46倍。PEG/PLA双层膜中PLA球晶的生长速率随结晶温度的升高均呈先升高后降低的变化趋势。此外,PEG/PLA双层膜中,聚乳酸球晶呈环带球晶且成核密度显著提高。DSC测试表明,随着PEG膜厚的增加,PEG/PLA双层膜的玻璃化转变温度降低。

A series of poly( ethylene glycol)/polylactide( PEG/PLA) double-layer films with different thicknesses of PEG film were prepared. The crystal morphology,growth rate of spherulitesand thermal property for the beneath PLA layer in PEG/PLA double-layer films with different thicknesses of PEG film during isothermal crystallization at various temperatures were studied by using polarized optical microscopy( POM) and differential scanning calorimetry( DSC). The results showed that the top covering molten PEG layer could obviously accelerate the spherulitic growth rate( G) of the beneath PLA layer and PEG layer with 2 mm film showed the fastest growth rate,the fastest growth rate of PLA spherulites in PEG/PLA double-layer films was 23. 0 mm/min,which is about 46 times of neat PLA with growth rate of 0. 5 mm/min. With the increase of crystallization temperature,each crystal growth rate of PLA in PEG/PLA double-layer films showed a trend of rising first and then falling. In addition,PLA spherulites in PEG/PLA double-layer films showed ring-banded texture and the nucleation density of PLA spherulite in PEG/PLA double-layer films increased dramatically. DSC date showed that the glass transition temperature( T_g) reduced with the increase of thickness of PEG film.